Third-harmonic generation in an AlGaAs/AlAs superlattice

Abstract
Third‐harmonic generation in an AlGaAs/AlAs superlattice is observed for the first time at a pump‐light wavelength of around 2 μm. The value of third‐order optical susceptibility χ(3), for the polarization parallel to the superlattice layer in a nonresonant region, is close to that reported for bulk GaAs. Enhancement of χ(3), giving more than three times the nonresonant value, is observed near a three‐photon resonance region. A characteristic third‐harmonic signal is observed when the pump‐light polarization has a component perpendicular to the superlattice layer. This is considered to be another χ(3) enhancement which is caused by nonparabolicity in the superlattice.